Control apparatus of an electric motor

ABSTRACT

A method, according to the present invention, of adjusting control parameters used in a control apparatus of an electric motor includes the steps of: computing a first frequency characteristic (Step  1 ); computing a present speed-proportional gain range (Step  2 ); computing a present mechanical-system characteristic constant (Step  3 ); computing a present proportional gain range (Step  4 ); computing a secular characteristic (Step  5 ); computing a secular speed-proportional gain range (Step  6 ); computing a secular proportional gain range (Step  7 ); and selecting proportional gain values (Step  8 ).

TECHNICAL FIELD

The present invention relates to methods for adjusting controlparameters used in control apparatuses of electric motors. Moreover, thepresent invention also relates to control apparatuses of electric motorsin which the methods for adjusting the control parameters describedabove are used.

BACKGROUND ART

Conventionally, methods for adjusting control parameters have been knownfor use in control apparatuses of electric motors. Such methods includethe technology disclosed in Patent Literature 1, for example. Thecontrol apparatus disclosed in Patent Literature 1 calculates optimalcontrol parameters on the basis of gain characteristics and phasecharacteristics, by using frequency characteristics of a drive system.

FIG. 9 is a view of a configuration of a control apparatus of aconventional electric motor. Control apparatus 151 shown in FIG. 9 isone example of conventional technologies. Usually, when electric motor101 is driven, control apparatus 151 of the motor shown in FIG. 9operates such that switch 109 is connected to an a-side terminal. Atthis moment, parts involved in the apparatus perform the followingoperations.

That is, mechanical system 104 includes motor 101, load 102, and motorposition detector 103. Load 102 is driven by motor 101. Detectionposition θ_(m) of motor 101 is output from motor position detector 103.Speed computing unit 106 computes detection speed v_(m) of the motor,from the amount of variation per unit time in detection position θ_(m).Speed computing unit 106 outputs thus-computed detection speed v_(m) ofthe motor. Position controller 107 outputs speed command v_(r) such thatdetection position θ_(m) follows position command θ_(r). Positioncommand θ_(r) is inputted from the outside of control apparatus 151 ofthe motor. Speed controller 108 outputs torque command τ_(r) such thatdetection speed v_(m) of the motor follows speed command v_(r).Thus-output torque command τ_(r) turns to new torque command τ_(r2), viafilter 110. New torque command τ_(r2) is inputted to torque controller111. Motor 101 is controlled by the output from torque controller 111.

When the control parameters are adjusted, control apparatus 151 of themotor shown in FIG. 9 operates such that switch 109 is connected to ab-side terminal. At this moment, parts involved in the apparatus performthe following operations.

That is, torque command generator 112 for measuring frequencycharacteristics outputs first torque command τ_(r1). First torquecommand τ_(r1) contains a plurality of frequency components, such as amaximum length sequence (M-sequence) signal, for example. The M-sequencesignal is a random binary bit-string signal indicated as either 0/1 or−1/1. Motor 101 is driven in accordance with first torque commandτ_(r1). At this moment, first torque command τ_(r1) and detection speedv_(m) of the motor are inputted to control parameter adjuster 115.

Control parameter adjuster 115 computes frequency characteristics fromfirst torque command τ_(r1) to motor speed v_(m). Control parameteradjuster 115 computes a control parameter of speed controller 108, acontrol parameter of position controller 107, and a control parameter offilter 110, by using the computed frequency characteristics, such thatthe operations of the control system of the motor is stabilized and theresponsivity of the control system of the motor is enhanced. The controlsystem of the motor includes speed controller 108, position controller107, and filter 110.

CITATION LIST Patent Literature

PTL 1: Japanese Patent Unexamined Publication No. 2005-245051

SUMMARY OF THE INVENTION

A control apparatus, to which the present invention is applied, of anelectric motor includes a first position controller, a speed controller,a torque controller, and a torque command generator.

The first position controller generates a speed command such that aposition command transmitted from the outside of the control apparatusof the motor coincides with a load's detection position, i.e. a detectedposition of a load coupled with the motor.

The speed controller generates a torque command such that the speedcommand coincides with a motor's detection speed, i.e. a detected speedof the motor.

The torque controller drives the motor in accordance with the torquecommand.

The torque command generator outputs a for-adjustment torque commandwhich includes a plurality of frequency components.

In the motor's control apparatus to which the present invention isapplied, a speed feedback circuit and a first position feedback circuitare formed.

The speed feedback circuit includes the speed controller and the torquecontroller. The speed feedback circuit is a control loop in which amotor's detection speed to be re-input to the speed controller isacquired from both the speed command and the motor's detection speedwhich both have been inputted to the speed controller.

The first position feedback circuit includes the first positioncontroller and the speed feedback circuit. The first position feedbackcircuit is a control loop in which a load's detection position, i.e. adetected position of the load coupled with the motor, to be re-inputtedto the first position controller is acquired. This acquisition is madefrom both the detection position of the load coupled with the motor andthe position command which both have been inputted to the first positioncontroller.

A method, according to the present invention, of adjusting controlparameters used in the control apparatus of the motor described aboveincludes the steps of: computing a first frequency characteristic,computing a present speed-proportional gain range, computing a presentmechanical-system characteristic constant, computing a presentproportional gain range, computing a secular characteristic, computing asecular speed-proportional gain range, computing a secular proportionalgain range, and selecting proportional gains.

The step of computing the first frequency characteristic uses thefor-adjustment torque command and the motor's detection speed. Thefor-adjustment torque command is output from the torque commandgenerator. The motor's detection speed is detected when the motor isdriven in accordance with the for-adjustment torque command. The step ofcomputing the first frequency characteristic computes a presentload-frequency characteristic which is frequency characteristics fromthe for-adjustment torque command to the motor's detection speed.

The step of computing the present speed-proportional gain range uses aspeed-proportional gain and the present load-frequency characteristic.The speed-proportional gain is the control parameter used in the speedcontroller. The step of computing the present speed-proportional gainrange computes a range of a present speed-proportional gain of thespeed-proportional gain such that the speed feedback circuit becomesstable.

The step of computing the present mechanical-system characteristicconstant uses the present load-frequency characteristic. The step ofcomputing the present mechanical-system characteristic constant computesthe present mechanical-system characteristic constant which indicatescharacteristics of a mechanical system containing the motor and theload.

The step of computing the present proportional gain range uses thespeed-proportional gain, a position-proportional gain which is thecontrol parameter used in the first position controller, the presentload-frequency characteristic, and the present mechanical-systemcharacteristic constant. The step of computing the present proportionalgain range computes the present proportional gain range, which is arange of combination of the present speed-proportional gain and apresent position-proportional gain of the position-proportional gain,such that the position feedback circuit becomes stable.

The step of computing the secular characteristic computes a secularload-frequency characteristic and a secular mechanical-systemcharacteristic constant, on the basis of the present load-frequencycharacteristic and secular-change information transmitted from theoutside of the control apparatus of the motor. The secularload-frequency characteristic is a load frequency characteristic whichhas undergone a secular change. The secular mechanical-systemcharacteristic constant is a mechanical-system characteristic constantwhich has undergone the secular change.

The step of computing the secular speed-proportional gain range uses thespeed-proportional gain and the secular load-frequency characteristic.The step of computing the secular speed-proportional gain range computesthe secular speed-proportional gain range, which is a range of thespeed-proportional gain that has undergone the secular change, such thatthe speed feedback circuit becomes stable.

The step of computing the secular proportional gain range uses thespeed-proportional gain, the position-proportional gain, the secularload-frequency characteristic, and the secular mechanical-systemcharacteristic constant. The step of computing the secular proportionalgain range computes the secular proportional gain range, which is arange of combination of a secular speed-proportional gain and a secularposition-proportional gain, such that the first position feedbackcircuit becomes stable.

The step of selecting the proportional gains selects proportional gainsfrom computed-ranges. The proportional gains include a value of thespeed-proportional gain and a value of the position-proportional gain.The computed-ranges including: the present speed-proportional gainrange, the range of combination of the present speed-proportional gainand the present position-proportional gain, the secularspeed-proportional gain range, and the range of combination of thesecular speed-proportional gain and the secular position-proportionalgain. This selection is performed such that each value of the selectedproportional gains satisfies all of the corresponding computed-ranges.

The present speed-proportional gain range is computed in the step ofcomputing the present speed-proportional gain range. The range ofcombination of the present speed-proportional gain and the presentposition-proportional gain is computed in the step of computing thepresent proportional gain range. The secular speed-proportional gainrange is computed in the step of computing the secularspeed-proportional gain range. The range of combination of the secularspeed-proportional gain and the secular position-proportional gain iscomputed in the step of computing the secular proportional gain range.

In accordance with the present invention, the position of an end of theload coupled with the motor is directly detected, thereby computing theposition command by using the control apparatus in accordance with theresult of the detection. An object of the present invention is toprovide the method of adjusting the control parameters used in thecontrol apparatus of the motor such that the motor is controlled tofollow the computed position command.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a view of a configuration of a control apparatus of a motoraccording to a first embodiment of the present invention.

FIG. 2 is a block diagram of the control apparatus of the motoraccording to the first embodiment of the invention.

FIG. 3 is another block diagram of the control apparatus of the motoraccording to the first embodiment of the invention.

FIG. 4 is a flowchart illustrating control in the control apparatus ofthe motor according to the first embodiment of the invention.

FIG. 5 is a view of a configuration of a control apparatus of a motoraccording to a second embodiment of the present invention.

FIG. 6 is a block diagram of the control apparatus of the motoraccording to the second embodiment of the invention.

FIG. 7 is another block diagram of the control apparatus of the motoraccording to the second embodiment of the invention.

FIG. 8 is a flowchart illustrating control in a control apparatus of amotor according to a third embodiment of the present invention.

FIG. 9 is a view of a configuration of a control apparatus of aconventional motor.

DESCRIPTION OF EMBODIMENTS

A method of adjusting control parameters used in a control apparatus ofa motor, according to an embodiment of the present invention, is capableof calculating the control parameters, by using frequencycharacteristics, in the steps of calculation to be described later. Suchcomputed control parameters make it possible to achieve stability offully-closed control performed by the control apparatus and highresponsivity of the control apparatus. To calculate the controlparameters, the following two frequency characteristics are used. One isfrequency characteristics from a torque command to a motor speed, whichare obtained by using data from measurement operations. The other isfrequency characteristics which are obtained by modifying the frequencycharacteristics described above from a secular-change point of view.

Consequently, in the control apparatus of the motor in which thefully-closed control is adopted, the control parameters can be adjustedto achieve stable drive of the motor even if such a secular changeoccurs.

Like this, the control apparatus, having a configuration to be describedlater, of the motor according to the embodiment of the present inventionis capable of computing the control parameters by using frequencycharacteristics. Such computed control parameters make it possible toachieve the stability of the fully-closed control performed by thecontrol apparatus and the high responsivity of the control apparatus. Tocalculate the control parameters, the following two frequencycharacteristics are used. One is frequency characteristics from a torquecommand to a motor speed, which are obtained by using data frommeasurement operations. The other is frequency characteristics which areobtained by modifying the frequency characteristics described above froma secular-change point of view.

Consequently, in the control apparatus of the motor in which thefully-closed control is adopted, the control parameters can be adjustedto achieve the stable drive of the motor even if controlled objectsundergo any secular change in their characteristics. Such controlledobjects include the motor and loads connected to the motor.

That is to say, there have been the following problems to be solvedregarding the methods of adjusting the control parameters for use incontrol apparatuses of conventional electric motors, and regardingcontrol apparatuses of the conventional motors which adopt the methodsof adjusting the control parameters.

That is, the control apparatus of the conventional motor has adoptedso-called semi-closed control of the motor. The semi-closed controlincludes detecting the operation position of a movable element set inthe motor, and controlling the motor on the basis of the detectedoperation position of the movable element set in the motor. That is, thecontrol apparatus of the conventional motor has a configuration foradjusting the control parameters to perform the semi-closed control.Therefore, such a configuration cannot be applied to the controlapparatus that performs so-called fully-closed control in which theposition on the load side is controlled, with the load being connectedto the motor.

Moreover, when adjusting the control parameters, the control apparatusof the conventional motor uses the frequency characteristics of a drivesystem. The conventional method of adjusting the control parameters usesa result of measurement of the motor at the point in time when thefrequency characteristics are computed. In other words, if the controlapparatus of the motor has undergone the secular change, theconventional method of adjusting the control parameters is difficult toadjust the control parameters which can achieve stability of thecontrol. That is, the control apparatus of the conventional motorpossibly causes unstable control in the state where the controlapparatus of the motor has undergone the secular change. In this case,the control apparatus of the conventional motor needs to be re-adjusted.

In contrast to this, the method of adjusting the control parameters usedin the control apparatus of the motor according to the embodiment of thepresent invention, is applicable to the control apparatus which adoptsthe fully-closed control.

Moreover, the controlled objects of the control apparatus of the motorsometimes show variations in their characteristics due to their secularchanges. Even in this case, the adoption of the method of adjusting thecontrol parameters used in the control apparatus of the motor accordingto the embodiment of the invention, allows the control apparatus tostably drive the motor having the characteristics that have undergonethe secular change.

Likewise, the control apparatus of the motor, which adopts the method ofadjusting the control parameters according to the embodiment of theinvention, is capable of performing the fully-closed control. Asdescribed above, the control apparatus of the motor, which adopts themethod of adjusting the control parameters according to the embodimentof the invention, is capable of stably driving the motor even with thecharacteristics that have undergone the secular change.

Hereinafter, the embodiments of the present invention will be describedwith reference to the accompanying drawings. It is noted, however, thateach of the following embodiments is nothing more than an example forembodying the present invention, and is in no way intended to limit thetechnical scope of the invention.

Note that, the expression “a feedback circuit is stable” as referred toin the following descriptions means the state where, in a closed controlloop, a feedback value for a command value converges into a commandvalue.

In contrast, the expression “a feedback circuit is not stable,” that is,“the feedback circuit is in an unstable state” as referred tohereinafter means the state where, in a closed control loop, a feedbackvalue for a command value oscillates while the amplitude of theoscillation continues to increase.

Generally, whether the feedback circuit is in a stable state or anunstable state can be determined by detecting frequency characteristicsof the feedback circuit.

First Exemplary Embodiment

FIG. 1 is a view of a configuration of a control apparatus of anelectric motor according to a first embodiment of the present invention.FIG. 2 is a block diagram of the control apparatus of the motoraccording to the first embodiment of the invention. FIG. 3 is anotherblock diagram of the control apparatus of the motor according to thefirst embodiment of the invention. FIG. 4 is a flowchart illustratingcontrol in the control apparatus of the motor according to the firstembodiment of the invention.

In the following descriptions, the control apparatus of the motoraccording to the first embodiment of the invention will be exemplifiedto explain a method of adjusting control parameters used in the controlapparatus of the motor.

As shown in FIG. 1, control apparatus 30 of the motor according to thefirst embodiment of the invention includes: position controller 6serving as a first position controller; speed controller 7; torquecontroller 9; and torque command generator 10.

Position controller 6 generates speed command v_(r) such that positioncommand θ_(r), which is transmitted from the outside of controlapparatus 30 of the motor, coincides with load position θ_(L) which is adetected position of load 2 coupled with motor 1.

Speed controller 7 generates torque command τ_(r) such that speedcommand v_(r) coincides with motor speed v_(m) which is a detected speedof the motor.

Torque controller 9 drives motor 1 in accordance with torque commandτ_(r).

Torque command generator 10 outputs for-adjustment torque command τ_(r3)containing a plurality of frequency components.

In control apparatus 30 of the motor according to the first embodimentof the present invention, there are formed both speed feedback circuit40 and position feedback circuit 41 serving as a first position feedbackcircuit.

Speed feedback circuit 40 includes speed controller 7 and torquecontroller 9. Speed feedback circuit 40 is a control loop in which motorspeed v_(m) to be re-inputted to speed controller 7 is obtained fromboth speed command v_(r) and motor speed v_(m), i.e. a detected speed ofthe motor, with both having been inputted to speed controller 7.

Position feedback circuit 41 includes position controller 6 and speedfeedback circuit 40. Position feedback circuit 41 is a control loop inwhich load position θ_(L), which is a detected position of the loadcoupled with the motor and is to be re-input to position controller 6,is obtained from both position command θ_(r) and load position θ_(L),i.e. a detected position of load 2 coupled with motor 1, with bothhaving been inputted to position controller 6.

As shown in FIG. 4, the method, which is used in control apparatus 30 ofthe motor described above, of adjusting the control parameters accordingto the embodiment of the invention includes the steps of: computingfirst frequency characteristics (Step 1); computing a presentspeed-proportional gain range (Step 2); computing presentmechanical-system characteristic constants (Step 3); computing a presentproportional gain range (Step 4); computing secular characteristics(Step 5); computing a secular speed-proportional gain range (Step 6);computing a secular proportional gain range (Step 7); and selectingproportional gains (Step 8).

As shown in FIGS. 1, 3, and 4, the step (Step 1) of computing the firstfrequency characteristics uses motor speed v_(m) and for-adjustmenttorque command τ_(r3) which is output from torque command generator 10.The motor speed v_(m) is a motor's detection speed which is a detectedspeed of the motor detected when motor 1 is driven in accordance withfor-adjustment torque command τ_(r3). In the step (Step 1) of computingthe first frequency characteristics, present load-frequencycharacteristics are computed which are frequency characteristics fromfor-adjustment torque command τ_(r3) to motor speed v_(m), i.e. adetected speed of the motor.

The step (Step 2) of computing the present speed-proportional gain rangeuses the present load-frequency characteristics and speed-proportionalgain K_(v) which is a control parameter used in speed controller 7. Inthe step (Step 2) of computing the present speed-proportional gainrange, the present speed-proportional gain range is computed such thatspeed feedback circuit 40 becomes stable.

Note that, in the first embodiment, the expression “speed feedbackcircuit 40 is stable” as referred to herein means the state where motorspeed v_(m), which is a feedback value for speed command v_(r) servingas a command value, follows the speed command to converge into thecommand value.

The step (Step 3) of computing the present mechanical-systemcharacteristic constants uses the present load-frequencycharacteristics. In the step (Step 3) of computing the presentmechanical-system characteristic constants, the presentmechanical-system characteristic constants are computed which showcharacteristics of mechanical system 20 that includes motor 1 and load2.

The step (Step 4) of computing the present proportional gain range usesspeed-proportional gain K_(v), position-proportional gain K_(p) servingas a control parameter used in position controller 6, the presentload-frequency characteristics, and the present mechanical-systemcharacteristic constants. In the step (Step 4) of computing the presentproportional gain range, a range of combination of the presentspeed-proportional gain and the present position-proportional gain iscomputed such that position feedback circuit 41 becomes stable.

Note that, in the first embodiment, the expression “position feedbackcircuit 41 is stable” as referred to herein means the state where loadposition θ_(L), which is a feedback value for position command θ_(r)serving as a command value, follows the speed command to converge intothe command value.

In the step (Step 5) of computing the secular characteristics, bothsecular load-frequency characteristics and secular mechanical-systemcharacteristic constants are computed, on the basis of the presentload-frequency characteristics and secular-change information which istransmitted from the outside of control apparatus 30 of the motor. Thesecular load-frequency characteristics are load-frequencycharacteristics which have undergone a secular change. The secularmechanical-system characteristic constants are mechanical-systemcharacteristic constants which have undergone the secular change.

The step (Step 6) of computing the secular speed-proportional gain rangeuses speed-proportional gain K_(v) and the secular load-frequencycharacteristics. In the step (Step 6) of computing the secularspeed-proportional gain range, the secular speed-proportional gain rangeis computed such that speed feedback circuit 40 becomes stable.

The step (Step 7) of computing the secular proportional gain range usesspeed-proportional gain K_(v), position-proportional gain K_(p), thesecular load-frequency characteristics, and the secularmechanical-system characteristic constants. In the step (Step 7) ofcomputing the secular proportional gain range, a range of combination ofthe secular speed-proportional gain and the secularposition-proportional gain is computed such that position feedbackcircuit 41 becomes stable.

In the step (Step 8) of selecting the proportional gains, a value of thespeed-proportional gain and a value of the position-proportional gainare selected from the following computed-ranges such that each value ofthe selected gains can satisfy all of the corresponding computed-ranges.Such computed-ranges includes: the present speed-proportional gainrange; the range of combination of the present speed-proportional gainand the present position-proportional gain; the secularspeed-proportional gain range; and the range of combination of thesecular speed-proportional gain and the secular position-proportionalgain.

The range of the present speed-proportional gain is computed by the stepof computing the present speed-proportional gain range. The range ofcombination of the present speed-proportional gain and the presentposition-proportional gain is computed by the step of computing thepresent proportional gain range. The range of the secularspeed-proportional gain is computed by the step of computing the secularspeed-proportional gain range. The range of combination of the secularspeed-proportional gain and the secular position-proportional gain iscomputed by the step of computing the secular proportional gain range.

The configuration which can provide particularly outstanding functionaleffects is as follows.

That is, in control apparatus 30 of the electric motor according to thefirst embodiment of the present invention, speed feedback circuit 40further includes electric motor 1, motor position detector 3, and speedcomputing unit 5.

Motor position detector 3 detects motor position θ_(m), i.e. a detectedposition of motor 1, and then outputs the detected motor position θ_(m).Speed computing unit 5 computes motor speed v_(m), i.e. a detected speedof the motor, on the basis of motor position θ_(m) that is output frommotor position detector 3.

In addition, position feedback circuit 41 serving as the first positionfeedback circuit further includes load 2 and load position detector 4.

Load position detector 4 detects load position θ_(L), i.e. a detectedposition of load 2, and then outputs the detected load position θ_(L).

Moreover, in the step (Step 8) of selecting the proportional gains, thevalues of both the speed-proportional gain and the position-proportionalgain may preferably be selected such that the largest speed-proportionalgain can be obtained.

Detailed descriptions will be further made with reference to theFigures.

As shown in FIG. 1, the device in which the first embodiment of thepresent invention is adopted includes control apparatus 30 of theelectric motor and mechanical system 20 driven by control apparatus 30of the motor. Note that, in the following descriptions, controlapparatus 30 of the electric motor is also referred to simply as controlapparatus 30.

First, mechanical system 20 to be driven includes motor 1, load 2, motorposition detector 3, and load position detector 4. Moreover, mechanicalsystem 20 includes coupling units between these parts. The couplingunits between these parts include: a coupling unit positioned betweenmotor 1 and load 2, a coupling unit positioned between motor 1 and motorposition detector 3, and a coupling unit positioned between load 2 andload position detector 4.

In mechanical system 20, motor 1 is coupled with load 2. Load 2 coupledwith motor 1 is driven by motor 1. Motor position detector 3 is coupledwith motor 1. Motor position detector 3 outputs motor position θ_(m)which is position information of motor 1. Load position detector 4 iscoupled with load 2. Load position detector 4 outputs load positionθ_(L) which is position information of load 2.

Here, load 2 is a device having a movable constituent element such as atable connected via a ball screw or a belt, for example. Motor positiondetector 3 is a sensor, such as an optical encoder or a resolver, todetect a rotation angle, for example. Load position detector 4 is asensor, such as a linear scale, to measure an amount of linear motion,for example.

Control apparatus 30 outputs a signal to drive motor 1, as describedlater. In control apparatus 30, speed computing unit 5 is inputted withmotor position θ_(m) which is output from motor position detector 3. Incontrol apparatus 30, speed computing unit 5 computes motor speed v_(m),i.e. a speed of motor 1, on the basis of inputted motor position θ_(m).Speed computing unit 5 outputs thus-computed motor speed v_(m).

In the first embodiment, speed feedback circuit 40 to be described lateris configured with speed controller 7, torque controller 9, motor 1,motor position detector 3, and speed computing unit 5. Likewise,position feedback circuit 41 is configured with position controller 6,speed feedback circuit 40, load 2, and load position detector 4.

Next, operations of control apparatus 30 according to the firstembodiment will be described in which the control apparatus drives motor1 to perform position control of load 2.

When the position control of load 2 is performed, switch 8 shown in FIG.1 is switched to an a-side terminal.

Control apparatus 30 is inputted with position command θ_(r) from theoutside of control apparatus 30. On the outside of control apparatus 30,a host controller and the like to generate position command θ_(r) isdisposed.

Position controller 6 is inputted with a difference between positioncommand θ_(r) and load position θ_(L) which is output from load positiondetector 4. Position controller 6 computes speed command v_(r) such thatposition command θ_(r) coincides with load position θ_(L). Positioncontroller 6 outputs thus-computed speed command v_(r). For example,position controller 6 performs a proportional operation expressed byfollowing Equation 1.

Note that, in Equation 1, Kp is the position-proportional gain.Equation 1v _(r) =K _(p)(θ_(r)−θ_(L))  (1)

Speed controller 7 is inputted with a difference between speed commandv_(r) and motor speed v_(m). Speed controller 7 computes torque commandτ_(r) such that speed command v_(r) coincides with motor speed v_(m).Speed controller 7 outputs thus-computed torque command τ_(r). Forexample, Speed controller 7 performs a proportional operation expressedby following Equation 2.

Note that, in Equation 2, K_(v) is the speed-proportional gain.Equation 2τ_(r) =K _(v)(v _(r) −v _(m))  (2)

Torque controller 9 converts inputted torque command τ_(r) into anelectric current command. Torque controller 9 performs electric currentcontrol such that a current that flows in motor 1 coincides with thecurrent command. Torque controller 9 performs the current control todrive motor 1.

In FIG. 2, J_(m) is the inertia of motor 1. Likewise, J_(L) is theinertia of load 2. Ks is the spring constant between motor 1 and load 2.D_(S) is the viscosity coefficient between motor 1 and load 2. D(s) isthe transfer function concerning a delay factor of the control system.

Moreover, “τ_(m)” is the torque applied to motor 1. “τ_(L)” is thetorque applied to load 2. “v_(L)” is the load speed that is a speed ofload 2. “τ_(in)” is the electric power supplied from control apparatus30, with the power expressing a torque generated by motor 1. “s” is theLaplace operator.

An equation of motion is derived on the basis of the block diagram shownin FIG. 2. By calculating the thus-derived equation of motion, thetransfer function of motor speed v_(m) can be calculated with respect totorque τ_(in) generated by motor 1. The transfer function of motor speedv_(m) with respect to torque τ_(in) generated by motor 1 is expressed byfollowing Equation 3.

$\begin{matrix}{{Equation}\mspace{14mu} 3} & \; \\\begin{matrix}{\frac{v_{m}}{\tau_{in}} = \frac{{J_{L} \cdot s^{2}} + {D_{s} \cdot s} + K_{s}}{{J_{m} \cdot J_{L} \cdot s^{3}} + {{D_{s}\left( {J_{m} + J_{L}} \right)} \cdot s^{2}} + {{K_{s}\left( {J_{m} + J_{L}} \right)} \cdot s}}} \\{= \frac{{\frac{J_{L}}{K_{s}}s^{2}} + {\frac{D_{s}}{K_{s}}s} + 1}{{\frac{J_{m}J_{L}}{K_{s}}s^{3}} + {\frac{D_{s}\left( {J_{m} + J_{L}} \right)}{K_{s}}s^{2}} + {\left( {J_{m} + J_{L}} \right) \cdot s}}}\end{matrix} & (3)\end{matrix}$

On the other hand, the coupling unit positioned between motor 1 and load2 offers spring constant K_(S) and viscosity coefficient D_(S). Springconstant K_(S) is a coefficient that indicates the degree of power ofrepulsion against torsion that occurs between motor 1 and load 2 whichare coupled with each other via the coupling unit. Viscosity coefficientD_(S) is a coefficient that indicates the degree of power of resistancein proportion to the speed of motor 1. For example, the power ofresistance includes friction.

Therefore, mechanical system 20 can be considered to be a two-inertiasystem having resonance angular frequency ω_(p) and anti-resonanceangular frequency ω_(z). In the two-inertia system, let ζ_(p) be theresonance damping coefficient and let ζ_(z) be the anti-resonancedamping coefficient. In this case, the transfer function of motor speedv_(m) with respect to torque τ_(in) generated by motor 1 is alsoexpressed by following Equation 4.

$\begin{matrix}{{Equation}\mspace{14mu} 4} & \; \\\begin{matrix}{\frac{v_{m}}{\tau_{in}} = {\frac{1}{\left( {J_{m} + J_{L}} \right) \cdot s} \cdot \frac{{\frac{1}{\omega_{z}^{2}}s^{2}} + {2\frac{\zeta_{z}}{\omega_{z}}s} + 1}{{\frac{1}{\omega_{p}^{2}}s^{2}} + {2\frac{\zeta_{p}}{\omega_{p}}s} + 1}}} \\{= \frac{{\frac{1}{\omega_{z}^{2}}s^{2}} + {2\frac{\zeta_{z}}{\omega_{z}}s} + 1}{{\frac{J_{m} + J_{L}}{\omega_{p}^{2}}s^{3}} + {2\frac{\zeta_{p}\left( {J_{m} + J_{L}} \right)}{\omega_{p}}s^{2}} + {\left( {J_{m} + J_{L}} \right) \cdot s}}}\end{matrix} & (4)\end{matrix}$

Moreover, an equation of motion is derived on the basis of the controlblock diagram shown in FIG. 2. By calculating the derived equation ofmotion, the transfer function of load speed v_(L) with respect to torqueτ_(in) generated by motor 1 can be computed. The transfer function ofload speed v_(L) with respect to torque τ_(in) generated by motor 1 isexpressed by following Equation 5.

$\begin{matrix}{{Equation}\mspace{14mu} 5} & \; \\\begin{matrix}{\frac{v_{L}}{\tau_{in}} = \frac{{D_{s} \cdot s} + K_{s}}{{J_{m}{J_{L} \cdot s^{3}}} + {{D_{s}\left( {J_{m} + J_{L}} \right)} \cdot s^{2}} + {{K_{s}\left( {J_{m} + J_{L}} \right)} \cdot s}}} \\{= \frac{{\frac{D_{s}}{K_{s}}s} + 1}{{\frac{J_{m}J_{L}}{K_{s}}s^{3}} + {\frac{D_{s}\left( {J_{m} + J_{L}} \right)}{K_{s}}s^{2}} + {\left( {J_{m} + J_{L}} \right) \cdot s}}}\end{matrix} & (5)\end{matrix}$

Equation 3 and Equation 5 described above are used to derive thetransfer function of load speed v_(L) with respect to motor speed v_(m).The thus-derived transfer function of load speed v_(L) with respect tomotor speed v_(m) is expressed by following Equation 6.

$\begin{matrix}{{Equation}\mspace{14mu} 6} & \; \\\begin{matrix}{\frac{v_{L}}{v_{m}} = \frac{{\frac{D_{s}}{K_{s}}s} + 1}{{\frac{J_{L}}{K_{s}}s^{2}} + {\frac{D_{s}}{K_{s}}s} + 1}} \\{= \frac{{\frac{2\zeta_{z}}{\omega_{z}}s} + 1}{{\frac{1}{\omega_{z}^{2}}s^{2}} + {\frac{2\zeta_{z}}{\omega_{z}}s} + 1}}\end{matrix} & (6)\end{matrix}$

Equation 3 and Equation 6 described above can be used to convert theblock diagram shown in FIG. 2 into the block diagram shown in FIG. 3.

In FIG. 3, L₁(s) is the transfer function of motor speed v_(m) withrespect to torque τ_(in) generated by motor 1. L₁(s) shown in FIG. 3equals Equation 3 described above. Moreover, in FIG. 3, L₂(s) is thetransfer function of load speed v_(L) with respect to motor speed v_(m).L₂(s) shown in FIG. 3 equals Equation 6 described above.

Position-proportional gain K_(p) and speed-proportional gain K_(v) arethe control parameters used in control apparatus 30 shown in FIG. 1.Accordingly, adjustment of both position-proportional gain K_(p) andspeed-proportional gain K_(v) can be performed through monitoring thestability of the frequency characteristics which are computed by usingthe transfer function derived from the block diagram shown in FIG. 3.

Next, descriptions will be made regarding the adjustment of bothposition-proportional gain K_(p) and speed-proportional gain K_(v),which both are the control parameters used in control apparatus 30, withreference to the flowchart shown in FIG. 4. Note that, all of the stepsin the flowchart shown in FIG. 4 can be performed with control parameteradjuster 11.

When the control parameters are adjusted, switch 8 shown in FIG. 1 isswitched to a b-side terminal. At this moment, for example,for-adjustment torque command τ_(r3) is output to torque controller 9from torque command generator 10 for measuring the frequencycharacteristics. For-adjustment torque command τ_(r3) contains aplurality of frequency components such as an M-sequence signal. Motor 1is driven in accordance with for-adjustment torque command τ_(r3).

At this moment, as shown in FIG. 4, both for-adjustment torque commandτ_(r3) and motor speed v_(m) are sampled by control parameter adjuster11. Control parameter adjuster 11 computes the frequency characteristicsfrom for-adjustment torque command τ_(r3) to motor speed v_(m) (Step 1).Hereinafter, the thus-computed frequency characteristics are referred toas “load-frequency characteristics.” The load-frequency characteristicsindicate the present load-frequency characteristics.

The load-frequency characteristics can be computed by the followingprocedure. For example, each of sampled for-adjustment torque commandτ_(r3) and sampled motor speed v_(m) is subjected to Fouriertransformation. The Fourier transformation of motor speed v_(m) resultsin the computation of both gain characteristics and phasecharacteristics. Like this, the Fourier transformation of for-adjustmenttorque command τ_(r3) results in the computation of both gaincharacteristics and phase characteristics. The load-frequencycharacteristics are derived by subtracting the gain characteristics andphase characteristics which have been computed on the basis offor-adjustment torque command τ_(r3), from the gain characteristics andphase characteristics which have been computed on the basis of motorspeed v_(m). The thus-derived load-frequency characteristics areD(s)·L₁(s) shown in FIG. 3.

Next, speed-proportional gain K_(v) is varied to compute a range ofspeed-proportional gain K_(v) such that speed feedback circuit 40 shownin FIG. 3 becomes stable (Step 2). The thus-computed range ofspeed-proportional gain K_(v) indicates the range of presentspeed-proportional gain K_(v).

Speed-proportional gain K_(v) is the control parameter of speedcontroller 7 shown in FIG. 1. In FIG. 3, speed feedback circuit 40 issurrounded by the dash-dot line.

For example, for speed feedback circuit 40 surrounded by the dash-dotline, the load-frequency characteristics of D(s)·L₁(s) are determined inStep 1. The thus-determined load-frequency characteristics aremultiplied by speed-proportional gain K_(v) to compute open-loopfrequency characteristics in speed feedback circuit 40. A range, whichallows speed feedback circuit 40 to be stable, of speed-proportionalgain K_(v) can be computed by such as a procedure of judging thestability of an open loop, with the procedure being described in PatentLiterature 1.

Next, the load-frequency characteristics can be used to compute themechanical-system characteristic constants which express thecharacteristics of the mechanical system (Step 3). The thus-computedmechanical-system characteristic constants indicate the presentmechanical-system characteristic constants.

The mechanical-system characteristic constants include, for example, theresonance angular frequency, anti-resonance angular frequency, resonancedamping coefficient, and anti-resonance damping coefficient. Themechanical-system characteristic constants can be computed by thefollowing procedure, as one example: That is, the characteristics ofknown delay factor D(s) are subtracted from the load-frequencycharacteristics, thereby determining the characteristics of transferfunction L₁(s) of motor speed v_(m) with respect to torque τ_(in)generated by motor 1. The mechanical-system characteristic constants canbe computed by applying the least squares method or the like to thethus-determined characteristics of transfer function L₁(s) of motorspeed v_(m).

Next, both speed-proportional gain K_(v) and position-proportional gainK_(p) are varied to compute a range of combination of speed-proportionalgain K_(v) and position-proportional gain K_(p) such that positionfeedback circuit 41 becomes stable (Step 4). The thus-computed range ofcombination of speed-proportional gain K_(v) and position-proportionalgain K_(p) indicates the range of combination of presentspeed-proportional gain K_(v) and present position-proportional gainK_(p).

Speed-proportional gain K_(v) is the control parameter of speedcontroller 7. Position-proportional gain K_(p) is the control parameterof position controller 6.

In FIG. 3, position feedback circuit 41 is the whole of the controlblock.

As described above, for example, once speed-proportional gain K_(v) isgiven, the frequency characteristics of speed feedback circuit 40 can becomputed by using the procedure described in Step 2.

Moreover, use of the mechanical-system characteristic constantsdetermined in Step 3 allows the determination of transfer function L₂(s)of load speed v_(L) with respect to motor speed v_(m). Themechanical-system characteristic constants include: resonance angularfrequency ω_(p), anti-resonance angular frequency ω_(z), resonancedamping coefficient ζ_(p), and anti-resonance damping coefficient ζ_(z).

Here, the open-loop frequency characteristics of position feedbackcircuit 41 can be computed by connecting position-proportional gainK_(p), the frequency characteristics of speed feedback circuit 40, andtransfer function L₂(s). The range, which allows position feedbackcircuit 41 to be stable, of combination of speed-proportional gain K_(v)and position-proportional gain K_(p) can be computed by using aprocedure of judging the stability of an open loop, with the procedurebeing one described above or the like.

Next, descriptions will be made regarding a step of computing a stablegain in cases where a secular change has occurred.

In cases where control apparatus 30 shown in FIG. 1 has undergone thesecular change, the stiffness of elements included in the mechanicalsystem often decreases and the amount of friction of the elementsincluded in the mechanical system often changes. In cases of occurrenceof such a secular change, it is considered that the transfer functionswill change in the following values to be described later. That is,resonance angular frequency ω_(p) and anti-resonance angular frequencyω_(z) will decrease. Resonance damping coefficient ζ_(p) andanti-resonance damping coefficient ζ_(z) will change as follows.

That is, as the friction increases, both resonance damping coefficientζ_(p) and anti-resonance damping coefficient ζ_(z) increase. Incontrast, as the friction decreases, both resonance damping coefficientζ_(p) and anti-resonance damping coefficient ζ_(z) decrease.

Consequently, concerning the elements included in the mechanical system,effects of such a secular change are examined, in advance, on the degreeof how much a change will occur in each of resonance angular frequencyω_(p), anti-resonance angular frequency ω_(z), resonance dampingcoefficient ζ_(p), and anti-resonance damping coefficient ζ_(z). Thisexamination allows the determination of the load-frequencycharacteristics after the secular change has occurred, and allows thedetermination of transfer function L₂(s) of load speed v_(L) withrespect to motor speed v_(m) after the secular change has occurred.

The load-frequency characteristics and transfer function L₂(s) of loadspeed v_(L) with respect to motor speed v_(m), both after the secularchange has occurred, can be computed by substituting, for Equations 4and 6, pre-examined resonance angular frequency ω_(p), pre-examinedanti-resonance angular frequency ω_(z), pre-examined resonance dampingcoefficient ζ_(p), and pre-examined anti-resonance damping coefficientζ_(z).

As described above, in cases of the secular change having occurred, thestep of computing the stable gain range is started by determining theload-frequency characteristics after the secular change has occurred,and by determining transfer function L₂(s) of load speed v_(L) withrespect to motor speed v_(m) after the secular change has occurred (Step5). The load-frequency characteristics after the secular change hasoccurred indicate the secular load-frequency characteristics.

Pre-examined information is used to determine the load-frequencycharacteristics after the secular change has occurred and to determinetransfer function L₂(s) of load speed v_(L) with respect to motor speedv_(m) after the secular change has occurred. Such pre-examinedinformation includes the degree of how much a change will occur in eachof resonance angular frequency ω_(p), anti-resonance angular frequencyω_(z), resonance damping coefficient ζ_(p), and anti-resonance dampingcoefficient ζ_(z).

Next, in a similar way to Steps 2 and 4, both the range ofspeed-proportional gain K_(v) and the range of combination ofspeed-proportional gain K_(v) and position-proportional gain K_(p) arecomputed by using the load-frequency characteristics and transferfunction L₂(s) which both are computed in Step 5. Speed-proportionalgain K_(v) is the control parameter of speed controller 7, and allowsthe speed controller to be stable. Position-proportional gain K_(p) isthe control parameter of position controller 6 (Step 6, Step 7). Thethus-computed range of speed-proportional gain K_(v) indicates the rangeof secular speed-proportional gain K_(v); the thus-computed range ofcombination of speed-proportional gain K_(v) and position-proportionalgain K_(p) is the range of combination of secular speed-proportionalgain K_(v) and secular position-proportional gain K_(p).

Finally, values of the speed-proportional gain and theposition-proportional gain are selected from the range ofspeed-proportional gain K_(v) and the range of position-proportionalgain K_(p), provided that each of the selected values can satisfy all ofthe respective ranges consisting of: the ranges of speed-proportionalgain K_(v); and the ranges of combination of speed-proportional gainK_(v) and position-proportional gain K_(p), with the respective rangeshaving been computed in Steps 2, 4, 6, and 7 (Step 8).

For example, one way of the selection may be such that the values of thegains are selected to maximize speed-proportional gain K_(v). Therefore,in the control apparatus of the motor in which the fully-closed controlis performed, it is possible to adjust the control parameters which canprovide stable drive even in cases where the secular change hasoccurred.

Second Exemplary Embodiment

Descriptions of another embodiment of the present invention will bemade.

Note that, in the descriptions hereinafter of a second embodiment, partshaving the same configurations as those shown in the first embodimentdescribed above are designated by the same numerals and symbols, and thecontents of their descriptions are incorporated herein by reference.

FIG. 5 is a view of a configuration of a control apparatus of anelectric motor according to the second embodiment of the presentinvention. FIG. 6 is a block diagram of the control apparatus of themotor according to the second embodiment of the invention. FIG. 7 isanother block diagram of the control apparatus of the motor according tothe second embodiment of the invention.

Differences in configuration are as follows, between control apparatus30 a of the motor according to the second embodiment and controlapparatus 30 of the motor according to the first embodiment describedabove.

That is, as shown in FIG. 5, control apparatus 30 a of the motoraccording to the second embodiment of the present invention includes:position controller 6 a serving as a second position controller, speedcontroller 7, torque controller 9, and torque command generator 10.

Position controller 6 a generates speed command v_(r) such that positioncommand θ_(r), which is transmitted from the outside of controlapparatus 30 of the motor, coincides with load position θ_(m) that is adetected position of motor 1.

Speed controller 7 generates torque command τ_(r) such that speedcommand v_(r) coincides with motor speed v_(m) that is a detected speedof the motor.

Torque controller 9 drives motor 1 in accordance with torque commandτ_(r).

Torque command generator 10 outputs for-adjustment torque command τ_(r3)which contains a plurality of frequency components.

In control apparatus 30 a of the motor according to the secondembodiment of the invention, there are formed speed feedback circuit 40and position feedback circuit 41 a serving as a second position feedbackcircuit.

Speed feedback circuit 40 includes speed controller 7 and torquecontroller 9. Speed feedback circuit 40 is a control loop in which motorspeed v_(m) to be re-inputted to speed controller 7 is obtained fromboth speed command v_(r) and motor speed v_(m), i.e. a detected speed ofthe motor, with both having been inputted to speed controller 7.

In the second embodiment, speed feedback circuit 40 includes: speedcontroller 7, torque controller 9, motor 1, motor position detector 3,and speed computing unit 5.

Position feedback circuit 41 a includes position controller 6 a andspeed feedback circuit 40. Position feedback circuit 41 a is a controlloop in which load position θ_(L), which is a detected position of themotor and is to be re-input to position controller 6 a, is obtained fromboth position command θ_(r) and load position θ_(L), i.e. a detectedposition of motor 1, with both having been inputted to positioncontroller 6.

In the second embodiment, position feedback circuit 41 a includesposition controller 6 a and speed feedback circuit 40.

Moreover, in the second embodiment, the expression “position feedbackcircuit 41 a is stable” as referred to herein means the state wheremotor position θ_(m), which is a feedback value for position commandθ_(r) serving as a command value, follows the position command toconverge into the command value.

That is, in the first embodiment described above, the descriptions weremade regarding the method of adjusting the control parameters of thecontrol apparatus of the motor in which the fully-closed control isperformed. According to the method of adjusting the control parameters,the motor can be stably driven even if the secular change has occurred.

On the other hand, in the second embodiment, the method of adjusting thecontrol parameters used in the control apparatus of the motor can alsobe applied to the control apparatus of a motor in which semi-closedcontrol is performed.

Detailed descriptions will be made further, with reference to theFigures.

As shown in FIG. 5, the apparatus according to the second embodimentincludes control apparatus 30 a of the motor and mechanical system 20 awhich is driven by control apparatus 30 a of the motor. Note that, inthe following descriptions, control apparatus 30 a of the motor is alsoreferred to simply as control apparatus 30 a.

A major difference between the second embodiment and the firstembodiment described above lies in their mechanical systems which arethe controlled objects. Mechanical system 20 a according to the secondembodiment includes motor 1 in which the semi-closed control isperformed.

As shown in FIGS. 5 to 7 and FIG. 4 incorporated herein by reference,control apparatus 30 a of the second embodiment is capable of adjustingthe control parameters by using motor position θ_(m) instead of loadposition θ_(L) that is used in the first embodiment.

Therefore, for the control apparatus of the motor in which thesemi-closed control is performed, use of the method of adjusting thecontrol parameters according to the second embodiment makes it possibleto adjust the control parameters which permit stable drive of the motoreven if the secular change has occurred.

Third Exemplary Embodiment

Further another embodiment of the present invention will be described.

Note that, in the descriptions hereinafter of a third embodiment, partshaving the same configurations as those shown in the first and secondembodiments described above are designated by the same numerals andsymbols, and the contents of their descriptions are incorporated hereinby reference.

FIG. 8 is a flowchart illustrating control in a control apparatus of anelectric motor according to the third embodiment of the presentinvention.

There exist differences in procedure between a method of adjustingcontrol parameters used in the control apparatus of the motor accordingto the third embodiment and the methods of adjusting the controlparameters used in the control apparatuses of the motors according tothe first and second embodiments described above. Such differences areas follows.

That is, as shown in FIG. 8, the method of adjusting the controlparameters used in the control apparatus of the motor according to thethird embodiment of the present invention is as follows: In a step (Step1 a) of computing second frequency characteristics, presentload-frequency characteristics are acquired which are frequencycharacteristics from for-adjustment torque command τ_(r3) to a detectedspeed of the motor.

With the flowchart according to the first embodiment described above, ithas been described that the following process is performed in Step 1.

That is, first, both for-adjustment torque command τ_(r3) and motorspeed v_(m) are sampled by control parameter adjuster 11. In controlparameter adjuster 11, thus-sampled for-adjustment torque command τ_(r3)and thus-sampled motor speed v_(m) are subjected to Fouriertransformation to compute load-frequency characteristics.

In accordance with the method, to be described later, of adjusting thecontrol parameters according to the third embodiment, the followingprocedure is possible in place of Step 1.

That is, as shown in FIG. 8, control parameter adjuster 11 is inputtedwith data after the Fourier transformation, thereby acquiring theload-frequency characteristics. The acquired load-frequencycharacteristics are used to perform computations in Step 2 andsubsequent ones.

Alternatively, load-frequency characteristics which have been computedin advance (Step 1 a) are used to perform the computations in Step 2 andsubsequent ones.

The method of adjusting the control parameters according to the thirdembodiment can be used in both control apparatuses, that is, the controlapparatus of the motor performing the fully-closed control described inthe first embodiment and the control apparatus of the motor performingthe semi-closed control described in the second embodiment.

Moreover, the way of selection in Step 8 may be such that the gainvalues are selected to maximize speed-proportional gain K_(v).Therefore, in both of the control apparatus of the motor performing thefully-closed control and the control apparatus of the motor performingthe semi-closed control, the adjustment of their control parameters canbe made to provide stable drive even in cases where the secular changehas occurred.

Note that, in Step 8 according to each of the embodiments describedabove, it has been described that the gain values may be selected tomaximize speed-proportional gain K_(v). However, speed-proportional gainK_(v) is not limited to the maximized value as long as a stable gainvalue can be selected. Instead, the speed-proportional gain may beanother value selected by a user.

Moreover, in the descriptions of the first embodiment, the embodimenthas been exemplified by the case where the mechanical system is atwo-inertia system. The present invention can be applied to the caseswhere the mechanical system is a multi-inertia system such as athree-inertia system. The present invention is capable of providing thesame advantageous effects even in the cases where the mechanical systemis a multi-inertia system such as a three-inertia system.

In addition, in Steps 2, 4, 6, and 7 in the first embodiment, it hasbeen described that the gain, which allows the speed feedback circuit tobe stable, is computed by a procedure of, such as, judging the stabilityof an open loop, with the procedure being described in Patent Literature1.

Note that the procedure of judging the stability of an open loop is usedin the descriptions, which is one described in Patent Literature 1;however, other procedures may also be used including the following one,for example. That is, the procedure includes: calculating the frequencycharacteristics of a closed loop which the feedback circuit has,determining a gain peak of the calculated frequency characteristics ofthe closed loop, and then judging that the loop is stable when the gainpeak is not larger than a predetermined value.

As can be seen clearly from the aforementioned descriptions, inaccordance with the embodiments of the present invention, both thespeed-proportional gain and the position-proportional gain are obtainedfrom the two states of operation, in order to extract the controlparameters used in the control apparatus of the electric motor. One is astate of operation of the present mechanical system, and the other is anexpected state of operation of the mechanical system after the apparatushas undergone the secular change.

The method of extracting the control parameters according to theembodiment can be used in both types of control apparatuses, that is,the control apparatus of the motor performing the fully-closed controland the control apparatus of the motor performing the semi-closedcontrol.

INDUSTRIAL APPLICABILITY

The method of adjusting the control parameters used in the controlapparatuses of the electric motors according to the present invention isuseful for both types of control apparatuses of the motors performingthe fully-closed control and control apparatuses of the motorsperforming the semi-closed control, when adjusting the controlparameters of the control apparatuses that have undergone the secularchange.

REFERENCE MARKS IN THE DRAWINGS

-   -   1, 101 motor    -   2, 102 load    -   3, 103 motor position detector    -   4 load position detector    -   5, 106 speed computing unit    -   6, 6 a, 107 position controller (first position controller,        second position controller)    -   7, 108 speed controller    -   8, 109 switch    -   9, 111 torque controller    -   10, 112 torque command generator    -   11, 115 control parameter adjuster    -   20, 20 a, 104 mechanical system    -   30, 30 a, 151 control apparatus (control apparatus of motor)    -   40 speed feedback circuit    -   41, 41 a position feedback circuit (first position feedback        circuit, second position feedback circuit)    -   110 filter

The invention claimed is:
 1. A control apparatus of an electric motor,the control apparatus including: a first position controller forgenerating a speed command such that a position command transmitted froman outside of the control apparatus of the motor coincides with a load'sdetection position that is a detected position of a load coupled withthe motor; a speed controller for generating a torque command such thatthe speed command coincides with a motor's detection speed that is adetected speed of the motor; a torque controller for driving the motorin accordance with the torque command; and a torque command generatorfor outputting a for-adjustment torque command containing a plurality offrequency components, wherein a speed feedback circuit serving as acontrol loop is formed including the speed controller and the torquecontroller, the speed feedback circuit acquiring a motor's detectionspeed to be re-inputted to the speed controller, the motor's detectionspeed to-be-re-inputted being acquired from the speed command and themotor's detection speed, the speed command and the motor's detectionspeed having been inputted to the speed controller, wherein a firstposition feedback circuit serving as a control loop is formed includingthe first position controller and the speed feedback circuit, the firstposition feedback circuit acquiring a load's detection position to bere-inputted to the first position controller, the load's detectionposition to-be-re-inputted being acquired from the position command andthe load's detection position, the position command and the load'sdetection position having been inputted to the first positioncontroller, where the load's detection position is a detected positionof a load coupled with the motor, and wherein the control apparatus isconfigured to: compute a present load-frequency characteristic by usingthe for-adjustment torque command output from the torque commandgenerator of the control apparatus and by using the motor's detectionspeed detected when the electric motor is driven in accordance with thefor-adjustment torque command, the present load-frequency characteristicbeing a frequency characteristic from the for-adjustment torque commandto the motor's detection speed; compute a present speed-proportionalgain range by using a speed-proportional gain and the presentload-frequency characteristic such that the speed feedback circuit ofthe control apparatus becomes stable, the present speed-proportionalgain range being a range of a present speed-proportional gain of thespeed-proportional gain serving as the control parameter used in thespeed controller of the control apparatus; compute a presentmechanical-system characteristic constant by using the presentload-frequency characteristic, the present mechanical-systemcharacteristic constant indicating a characteristic of a mechanicalsystem containing the electric motor and a load coupled with theelectric motor; compute a present proportional gain range by using thespeed-proportional gain, a position-proportional gain serving as thecontrol parameter used in the first position controller, the presentload-frequency characteristic, and the present mechanical-systemcharacteristic constant such that a first position feedback circuit ofthe control apparatus becomes stable, the present proportional gainrange being a range of a combination of the present speed-proportionalgain and a present position-proportional gain of theposition-proportional gain; compute a secular characteristic based onthe present load-frequency characteristic and secular-change informationtransmitted from an outside of the control apparatus of the electricmotor, wherein the secular characteristic includes a secularload-frequency characteristic, and a secular mechanical-systemcharacteristic constant, the secular load-frequency characteristic beingthe load-frequency characteristic having undergone a secular change andthe secular mechanical-system characteristic constant being amechanical-system characteristic constant having undergone the secularchange; compute a secular speed-proportional gain range by using thespeed-proportional gain and the secular load-frequency characteristicsuch that the speed feedback circuit becomes stable; compute a secularproportional gain range by using the speed-proportional gain, theposition-proportional gain, the secular load-frequency characteristic,and the secular mechanical-system characteristic constant such that thefirst position feedback circuit becomes stable, wherein the secularproportional gain range is a range of a combination of a secularspeed-proportional gain and a secular position-proportional gain, thesecular speed-proportional gain being the speed-proportional gain havingundergone the secular change and the secular position-proportional gainbeing the position-proportional gain having undergone the secularchange; select proportional gains from computed-ranges, the proportionalgains including a value of the speed-proportional gain and a value ofthe position-proportional gain, the computed-ranges including: thepresent speed-proportional gain range; the range of the combination ofthe present speed-proportional gain and the presentposition-proportional gain; the secular speed-proportional gain range;and the range of the combination of the secular speed-proportional gainand the secular position-proportional gain, wherein each value of theselected proportional gains satisfies all of the correspondingcomputed-ranges; and control the load's detection position that is thedetected position of the load coupled with the motor.
 2. The controlapparatus according to claim 1, wherein the speed feedback circuitfurther includes: the motor; a motor position detector for detecting amotor's detection position that is a detected position of the electricmotor, and outputting the detected motor's detection position; and aspeed computing unit for computing the motor's detection speed based onthe detected motor's detection position output from the motor positiondetector of the control apparatus, wherein the first position feedbackcircuit further includes: the load; and a load position detector fordetecting the load's detection position and outputting the detectedload's detection position.
 3. The control apparatus according to claim1, wherein the control apparatus is further configured to select thevalue of the speed-proportional gain and the value of theposition-proportional gain such that a largest speed-proportional gainis obtained, in the step of selecting the proportional gains.